drm/i915: Simplify control flow in intel_atomic_check a bit.

- Unconditionally add plane states. Core helpers would have done this
  in drm_atomic_helper_check_modeset, doing it once more won't cause
  harm and is less fragile.

- Simplify the continue logic when disabling a pipe.

Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1462779085-2458-1-git-send-email-daniel.vetter@ffwll.ch

drivers/gpu/drm/i915/intel_display.c

@@ -13351,15 +13351,14 @@ static int intel_atomic_check(struct drm_device *dev,
 		if (crtc_state->mode.private_flags != crtc->state->mode.private_flags)
 			crtc_state->mode_changed = true;
 
+		if (!needs_modeset(crtc_state))
+			continue;
+
 		if (!crtc_state->enable) {
-			if (needs_modeset(crtc_state))
 			any_ms = true;
 			continue;
 		}
 
-		if (!needs_modeset(crtc_state))
-			continue;
-
 		/* FIXME: For only active_changed we shouldn't need to do any
 		 * state recomputation at all. */
 
@@ -13382,13 +13381,12 @@ static int intel_atomic_check(struct drm_device *dev,
 			to_intel_crtc_state(crtc_state)->update_pipe = true;
 		}
 
-		if (needs_modeset(crtc_state)) {
+		if (needs_modeset(crtc_state))
 			any_ms = true;
 
 		ret = drm_atomic_add_affected_planes(state, crtc);
 		if (ret)
 			return ret;
-		}
 
 		intel_dump_pipe_config(to_intel_crtc(crtc), pipe_config,
 				       needs_modeset(crtc_state) ?